#include <bits/stdc++.h>

using namespace std;
const int N = 1010;

int m, n;
int f[N];
int v[N], w[N];
int main()
{
    cin >> m >> n;
    for (int i = 1; i <= n; ++i)
    {
        cin >> v[i] >> w[i];
        for (int j = m; j >= v[i]; --j)
        {
            f[j] = max(f[j], f[j - v[i]] + w[i]);
        }
    }
    cout << f[m] << endl;
    return 0;
}